1. Field of the Invention
The present invention relates to a tap for compressed or liquefied gases, and more particularly to a tap for compressed or liquefied gases which has an overcharging prevention function, in which a two-way valve permits high speed charging a gas through an opening opened at initial state until a gas storage tank is fully filled with the liquefied gas, regardless of pressure/level of the liquefied gas inside/outside a gas storage tank, and the tap, for higher charging efficiency in the gas storage tank, has a buffering disk permitting that a level-controlling valve does not interfere with operations of a cam and a float during the charging of the gas and that an abrupt drop of the level-controlling valve is prevented at the full-filling level, so that slow blocking of the gas supply is conducted.
2. Description of the Conventional Art
Apparatuses which use gas, such as liquefied petroleum gas (LPG), liquefied natural gas (LNG), compressed natural gas (CNG), etc., need to be recharged at a gas dispensing station when a gas storage tank of the apparatus is empty.
To prevent explosion possibly occurring due to the overcharging of gas when gas is recharged in the gas storage tank, it is required to provide a safety valve which, in the case of charging the gas with a certain level of a gas pressure, automatically operates by the gas pressure in the gas storage tank and is then operated to externally discharge the overcharged gas.
For a proper operation of the safety valve, the filling level of the liquefied gas to be filled in the gas storage tank has to be retained at a certain level so that a gaseous zone can be formed at the upper side.
A prior art relating to the tap for compressed or liquefied gases has been disclosed in U.S. Pat. No. 5,282,496 issued on Feb. 1, 1994, entitled "Tap for Compressed or Liquefied". Referring to FIG. 1, the tap for compressed or liquefied gases disclosed in the above-mentioned U.S. Pat. No. 5,282,496 will be described below.
As shown in FIG. 1, the tap for compressed or liquefied gases disclosed in the above-mentioned U.S. Pat. No. 5,282,496 comprises: an upper body 10 having an inlet channel 18 communicating with the inside of the body 10, the inlet channel providing a passage for flowing a gas introduced from the external, and having an outer lower part thereof provided with a screw thread 12 enabling the tap to be screwed onto a gas storage tank; an open/closure valve 14 and a packing 16 enabling manual open/closure of the inlet channel 18; and a safety valve 26 which enables the gases to externally escape through a passage 24 in the event of abnormal overpressure of the gas inside the gas storage tank.
Further, the tap for compressed or liquefied gases comprises: a lower body 32 coupled to the inside of the gas storage tank, having a lower side thereof provided with a two-way valve 30 having a chamber 38 inside, and a central portion whose both sides form the openings 34, 36; a piston 40 which slides in the chamber 38 by the pressure of the gas infused from the inlet channel 18, while maintaining the sealing by the seal 46 and the gasket 42, and having inside a passage 48 for introducing some portions of the infused gas; a spring 44 installed at a lower portion of the piston 40, for offering a restoration force allowing the piston 40 to return to its original position; an orifice 50 formed on a side surface of the lower body 32, operated to permit the remaining gas in the chamber 38 to flow to the gas storage tank; a level-controlling valve 52 movable up and down between the opened position defined by a washer 55 and the closure positions defined by the seal 54; a cam 56 rotatably supported by the arms 58, and for driving the level-controlling valve 52; a float 62 for driving the cam 56 by a descent/ascent motion depending upon the varying pressure (level) in the gas storage tank; and a two-way valve 30 installed between the passage 48 and the chamber 38, having a pendulum 64 serving to stop the gas supply through the channel 66 formed inside, when the tank is tilted.
A description will now be given of the operation of the conventional tap for compressed or liquefied gases as described above.
With the connector 22 being connected to a gas source outside the gas storage tank, a user opens the open/closure valve 14, so that the pressurized gas penetrates through the inlet channel 18. The pressurized gas pushes downward the piston 40 against the action of the spring 44, and the gas is infused into the gas storage tank through the openings 34, 36. Also, some portion of the gas penetrates through the passage 48 of the piston 40 to the lower part of the chamber 38 and flows around the level-controlling valve 52, in the compulsorily open position by the cam 56, into the gas storage tank.
As the tank fills up, the float 62 rises, thus resulting in a counter-clockwise pivoting of the cam 56. When the cam 56 pivots in a counter-clockwise direction, the top of the cam 56 brings into contact with a lower end of the valve 52, followed by the cam 56 starting to present a hollow part 56a to the level-controlling valve 52 and then a descent of the valve 52 through the effect of the pressure of the filling gas.
As a result, the level-controlling valve 52 comes into contact with the seal 54, which permits the stop of the gas supply into the gas storage tank through the level-controlling valve 52. The stop of the gas supply into the tank induces the increase in pressure inside the chamber 38 formed between the piston 40 and the level-controlling valve 52, and thus the piston 40 moves upward by the restoration force of the spring 44.
Consequently, the closure of the openings 34, 36 by the piston 40 stops the gas supply into the tank, which thus prevents the overcharging of the gas in order to maintain the preset level of the charged gas.
Meanwhile, the pendulum 64 serves to stop the gas supply through the channel 66 formed inside, when the tank is tilted.
However, since the above known tap for compressed or liquefied gases utilizes the scheme that the openings 34, 36 are opened when the pressure of the infused gas pushes downward the piston 40 supported against the spring 44 in order to infuse the gas, it needs to maintain the pressure above a certain level of the pressure. This causes a problem in that the size of the opening closely relating to the pressure of the gas is confined below a certain size.
In the case of the opening 34, 36 larger than a certain size, the reduction in the pressure of the gas by an amount corresponding to the increase in size of the opening presents, which induces partial closure of the opening caused by the rise of the piston 40 due to the restoration force of the spring 44. This results in the reduction in size of the opening. Therefore, there is a problem in that the charging speed is limited depending upon the size of the opening which is defined by the pressure of the gas and the restoration force of the spring.
Further, under non-loaded condition of the conventional tap for compressed or liquefied gases, the piston closes the inlet channel 18 by the action of the spring. At this time, when the handle is rotated to open the packing 16 in order to use the stored gas, only a single gas flow path for externally discharging the gas exists which path leads to the inner passage in the piston 48 through the passage between the nut 51 and the level-controlling valve 52.
In this case, since the diameter of the inner passage 48 is about 1.18 mm, maximum heat quantity permitted to be externally discharged is about 125,000 BTU/Hour, which quantity is considerably small. This means that a gas discharging quantity per time unit is small.
With such a retarded discharging/charging structure, a problem is caused in that a long time of about 12 minutes is taken to purge the empty gas storage tank, wherein the purging is needed to remove moisture vapor and air contained in the empty tank using four to five times the Freon-gas or LP-gas.
Moreover, during the gas charge using the above known tap for compressed or liquefied gases, the pressure of the charging gas is directly applied to the top surface of the level-controlling valve 52. Thus, the frictional force between the level-controlling valve and the cam 56 increases, which may interfere with the proper motions of the lever and the float 62 following the rise of the level of the liquefied gas.
Further, the hollow part 56a of the cam 56 almost resembles a U-shaped configuration, as shown in FIGS. 1 and 2. Therefore, immediately before a full charging level, there occurs a sudden drop of the level-controlling valve 52 by a distance corresponding to a fall height H, about 10 mm, of the cam 56 in order to prevent the overcharging of the gas. Further, such a level-controlling valve 52 in turn closes a passage between the nut 51 and the level-controlling valve 52, followed by the rise of the piston 48 which terminates the charging of the gas and an abrupt bounce of the float 62.
As a result, these phenomena yield problems in that even if there is room to further charge the gas in the gas storage tank, the gas supply is no longer further continued, thus resulting in the reduced charging efficiency due to deficiency of the gas by an amount corresponding to the fall height H.